An international team of scientists headed by author Dr. Rachel Huxley, Institute for International Health, University of Sydney, reviewed 18 studies covering a total of nearly 500,000 participants. The study was reported in a December issue of the Archives on Internal Medicine.
The authors acknowledged that while obesity and lack of physical activity point to the development of Type II diabetes, the roles of specific foods, drinks or diets is uncertain.
When the data from all of these studies (from 1966 to 2009) were analyzed, the scientists were able to reach some startling conclusions.
Drinking coffee was inversely related to risk of diabetes. In short, more coffee - lower risk. In fact so much so, that every extra cup of coffee consumed in a day was linked to a 7 per cent reduction in the excess risk of diabetes. For example, drinking 3 to 4 cups per day was linked to a 25 per cent lower risk than drinking none or up to two cups per day.
Drinking decaffeinated coffee, more than 3 to 4 cups a day, was linked to about one third lower risk of diabetes compared to none. And drinking more than 3 to 4 cups of tea per day was linked to a one fifth lower risk of diabetes compared to non-tea drinking.
The authors were both intrigued and wary of their conclusions, saying: "High intakes of coffee, decaffeinated coffee, and tea are associated with reduced risk of diabetes. The putative protective effects of these beverages warrant further investigation in randomized trials… (but) owing to the presence of small-study bias, our results may represent an overestimate of the true magnitude of the association".
There seemed to be little affect on the numbers whether the beverage was caffeinated or not. This seems to imply that caffeine is not the determining ingredient that lowers risk. Other compounds in coffee and tea, such as magnesium, antioxidants or chlorogenic acids, would be the more likely candidates which provide protection from developing diabetes.
"If such beneficial effects were observed in interventional trials to be real, the implications for the millions of individuals who have diabetes mellitus, or who are at future risk of developing it, would be substantial," they wrote.
“If we could find out what these active compounds are, we might find possible new ways of preventing type 2 diabetes,” they added. "It could also be envisaged that we will advise our patients most at risk for diabetes mellitus to increase their consumption of tea and coffee in addition to increasing their levels of physical activity and weight loss," wrote the authors
Some health officials fear that there may be over 380 million people with Type II diabetes in the world by 2025.